/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * Contributor(s): Blender Foundation
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/blenkernel/intern/mesh_tangent.c
 *  \ingroup bke
 *
 * Functions to evaluate mesh tangents.
 */

#include <limits.h>

#include "MEM_guardedalloc.h"

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"

#include "BLI_utildefines.h"
#include "BLI_math.h"
#include "BLI_stack.h"
#include "BLI_task.h"

#include "BKE_customdata.h"
#include "BKE_global.h"
#include "BKE_mesh.h"
#include "BKE_mesh_tangent.h"
#include "BKE_mesh_runtime.h"
#include "BKE_report.h"

#include "BLI_strict_flags.h"

#include "atomic_ops.h"
#include "mikktspace.h"


/* -------------------------------------------------------------------- */

/** \name Mesh Tangent Calculations (Single Layer)
 * \{ */

/* Tangent space utils. */

/* User data. */
typedef struct {
	const MPoly *mpolys;   /* faces */
	const MLoop *mloops;   /* faces's vertices */
	const MVert *mverts;   /* vertices */
	const MLoopUV *luvs;   /* texture coordinates */
	float (*lnors)[3];     /* loops' normals */
	float (*tangents)[4];  /* output tangents */
	int num_polys;         /* number of polygons */
} BKEMeshToTangent;

/* Mikktspace's API */
static int get_num_faces(const SMikkTSpaceContext *pContext)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	return p_mesh->num_polys;
}

static int get_num_verts_of_face(const SMikkTSpaceContext *pContext, const int face_idx)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	return p_mesh->mpolys[face_idx].totloop;
}

static void get_position(const SMikkTSpaceContext *pContext, float r_co[3], const int face_idx, const int vert_idx)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	const int loop_idx = p_mesh->mpolys[face_idx].loopstart + vert_idx;
	copy_v3_v3(r_co, p_mesh->mverts[p_mesh->mloops[loop_idx].v].co);
}

static void get_texture_coordinate(
        const SMikkTSpaceContext *pContext, float r_uv[2], const int face_idx,
        const int vert_idx)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	copy_v2_v2(r_uv, p_mesh->luvs[p_mesh->mpolys[face_idx].loopstart + vert_idx].uv);
}

static void get_normal(const SMikkTSpaceContext *pContext, float r_no[3], const int face_idx, const int vert_idx)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	copy_v3_v3(r_no, p_mesh->lnors[p_mesh->mpolys[face_idx].loopstart + vert_idx]);
}

static void set_tspace(
        const SMikkTSpaceContext *pContext, const float fv_tangent[3], const float face_sign,
        const int face_idx, const int vert_idx)
{
	BKEMeshToTangent *p_mesh = (BKEMeshToTangent *)pContext->m_pUserData;
	float *p_res = p_mesh->tangents[p_mesh->mpolys[face_idx].loopstart + vert_idx];
	copy_v3_v3(p_res, fv_tangent);
	p_res[3] = face_sign;
}

/**
 * Compute simplified tangent space normals, i.e. tangent vector + sign of bi-tangent one, which combined with
 * split normals can be used to recreate the full tangent space.
 * Note: * The mesh should be made of only tris and quads!
 */
void BKE_mesh_calc_loop_tangent_single_ex(
        const MVert *mverts, const int UNUSED(numVerts), const MLoop *mloops,
        float (*r_looptangent)[4], float (*loopnors)[3], const MLoopUV *loopuvs,
        const int UNUSED(numLoops), const MPoly *mpolys, const int numPolys,
        ReportList *reports)
{
	BKEMeshToTangent mesh_to_tangent = {NULL};
	SMikkTSpaceContext s_context = {NULL};
	SMikkTSpaceInterface s_interface = {NULL};

	const MPoly *mp;
	int mp_index;

	/* First check we do have a tris/quads only mesh. */
	for (mp = mpolys, mp_index = 0; mp_index < numPolys; mp++, mp_index++) {
		if (mp->totloop > 4) {
			BKE_report(reports, RPT_ERROR, "Tangent space can only be computed for tris/quads, aborting");
			return;
		}
	}

	/* Compute Mikktspace's tangent normals. */
	mesh_to_tangent.mpolys = mpolys;
	mesh_to_tangent.mloops = mloops;
	mesh_to_tangent.mverts = mverts;
	mesh_to_tangent.luvs = loopuvs;
	mesh_to_tangent.lnors = loopnors;
	mesh_to_tangent.tangents = r_looptangent;
	mesh_to_tangent.num_polys = numPolys;

	s_context.m_pUserData = &mesh_to_tangent;
	s_context.m_pInterface = &s_interface;
	s_interface.m_getNumFaces = get_num_faces;
	s_interface.m_getNumVerticesOfFace = get_num_verts_of_face;
	s_interface.m_getPosition = get_position;
	s_interface.m_getTexCoord = get_texture_coordinate;
	s_interface.m_getNormal = get_normal;
	s_interface.m_setTSpaceBasic = set_tspace;

	/* 0 if failed */
	if (genTangSpaceDefault(&s_context) == false) {
		BKE_report(reports, RPT_ERROR, "Mikktspace failed to generate tangents for this mesh!");
	}
}

/**
 * Wrapper around BKE_mesh_calc_loop_tangent_single_ex, which takes care of most boiling code.
 * \note
 * - There must be a valid loop's CD_NORMALS available.
 * - The mesh should be made of only tris and quads!
 */
void BKE_mesh_calc_loop_tangent_single(Mesh *mesh, const char *uvmap, float (*r_looptangents)[4], ReportList *reports)
{
	MLoopUV *loopuvs;
	float (*loopnors)[3];

	/* Check we have valid texture coordinates first! */
	if (uvmap) {
		loopuvs = CustomData_get_layer_named(&mesh->ldata, CD_MLOOPUV, uvmap);
	}
	else {
		loopuvs = CustomData_get_layer(&mesh->ldata, CD_MLOOPUV);
	}
	if (!loopuvs) {
		BKE_reportf(reports, RPT_ERROR, "Tangent space computation needs an UVMap, \"%s\" not found, aborting", uvmap);
		return;
	}

	loopnors = CustomData_get_layer(&mesh->ldata, CD_NORMAL);
	if (!loopnors) {
		BKE_report(reports, RPT_ERROR, "Tangent space computation needs loop normals, none found, aborting");
		return;
	}

	BKE_mesh_calc_loop_tangent_single_ex(
	        mesh->mvert, mesh->totvert, mesh->mloop, r_looptangents,
	        loopnors, loopuvs, mesh->totloop, mesh->mpoly, mesh->totpoly, reports);
}

/** \} */


/* -------------------------------------------------------------------- */

/** \name Mesh Tangent Calculations (All Layers)
 * \{ */


/* Necessary complexity to handle looptri's as quads for correct tangents */
#define USE_LOOPTRI_DETECT_QUADS

typedef struct {
	const float (*precomputedFaceNormals)[3];
	const float (*precomputedLoopNormals)[3];
	const MLoopTri *looptri;
	MLoopUV *mloopuv;   /* texture coordinates */
	const MPoly *mpoly;       /* indices */
	const MLoop *mloop;       /* indices */
	const MVert *mvert;       /* vertices & normals */
	const float (*orco)[3];
	float (*tangent)[4];    /* destination */
	int numTessFaces;

#ifdef USE_LOOPTRI_DETECT_QUADS
	/* map from 'fake' face index to looptri,
	 * quads will point to the first looptri of the quad */
	const int    *face_as_quad_map;
	int       num_face_as_quad_map;
#endif

} SGLSLMeshToTangent;

/* interface */
static int dm_ts_GetNumFaces(const SMikkTSpaceContext *pContext)
{
	SGLSLMeshToTangent *pMesh = pContext->m_pUserData;

#ifdef USE_LOOPTRI_DETECT_QUADS
	return pMesh->num_face_as_quad_map;
#else
	return pMesh->numTessFaces;
#endif
}

static int dm_ts_GetNumVertsOfFace(const SMikkTSpaceContext *pContext, const int face_num)
{
#ifdef USE_LOOPTRI_DETECT_QUADS
	SGLSLMeshToTangent *pMesh = pContext->m_pUserData;
	if (pMesh->face_as_quad_map) {
		const MLoopTri *lt = &pMesh->looptri[pMesh->face_as_quad_map[face_num]];
		const MPoly *mp = &pMesh->mpoly[lt->poly];
		if (mp->totloop == 4) {
			return 4;
		}
	}
	return 3;
#else
	UNUSED_VARS(pContext, face_num);
	return 3;
#endif
}

static void dm_ts_GetPosition(
        const SMikkTSpaceContext *pContext, float r_co[3],
        const int face_num, const int vert_index)
{
	//assert(vert_index >= 0 && vert_index < 4);
	SGLSLMeshToTangent *pMesh = pContext->m_pUserData;
	const MLoopTri *lt;
	uint loop_index;
	const float *co;

#ifdef USE_LOOPTRI_DETECT_QUADS
	if (pMesh->face_as_quad_map) {
		lt = &pMesh->looptri[pMesh->face_as_quad_map[face_num]];
		const MPoly *mp = &pMesh->mpoly[lt->poly];
		if (mp->totloop == 4) {
			loop_index = (uint)(mp->loopstart + vert_index);
			goto finally;
		}
		/* fall through to regular triangle */
	}
	else {
		lt = &pMesh->looptri[face_num];
	}
#else
	lt = &pMesh->looptri[face_num];
#endif
	loop_index = lt->tri[vert_index];

finally:
	co = pMesh->mvert[pMesh->mloop[loop_index].v].co;
	copy_v3_v3(r_co, co);
}

static void dm_ts_GetTextureCoordinate(
        const SMikkTSpaceContext *pContext, float r_uv[2],
        const int face_num, const int vert_index)
{
	//assert(vert_index >= 0 && vert_index < 4);
	SGLSLMeshToTangent *pMesh = pContext->m_pUserData;
	const MLoopTri *lt;
	uint loop_index;

#ifdef USE_LOOPTRI_DETECT_QUADS
	if (pMesh->face_as_quad_map) {
		lt = &pMesh->looptri[pMesh->face_as_quad_map[face_num]];
		const MPoly *mp = &pMesh->mpoly[lt->poly];
		if (mp->totloop == 4) {
			loop_index = (uint)(mp->loopstart + vert_index);
			goto finally;
		}
		/* fall through to regular triangle */
	}
	else {
		lt = &pMesh->looptri[face_num];
	}
#else
	lt = &pMesh->looptri[face_num];
#endif
	loop_index = lt->tri[vert_index];

finally:
	if (pMesh->mloopuv != NULL) {
		const float *uv = pMesh->mloopuv[loop_index].uv;
		copy_v2_v2(r_uv, uv);
	}
	else {
		const float *orco = pMesh->orco[pMesh->mloop[loop_index].v];
		map_to_sphere(&r_uv[0], &r_uv[1], orco[0], orco[1], orco[2]);
	}
}

static void dm_ts_GetNormal(
        const SMikkTSpaceContext *pContext, float r_no[3],
        const int face_num, const int vert_index)
{
	//assert(vert_index >= 0 && vert_index < 4);
	SGLSLMeshToTangent *pMesh = (SGLSLMeshToTangent *) pContext->m_pUserData;
	const MLoopTri *lt;
	uint loop_index;

#ifdef USE_LOOPTRI_DETECT_QUADS
	if (pMesh->face_as_quad_map) {
		lt = &pMesh->looptri[pMesh->face_as_quad_map[face_num]];
		const MPoly *mp = &pMesh->mpoly[lt->poly];
		if (mp->totloop == 4) {
			loop_index = (uint)(mp->loopstart + vert_index);
			goto finally;
		}
		/* fall through to regular triangle */
	}
	else {
		lt = &pMesh->looptri[face_num];
	}
#else
	lt = &pMesh->looptri[face_num];
#endif
	loop_index = lt->tri[vert_index];

finally:
	if (pMesh->precomputedLoopNormals) {
		copy_v3_v3(r_no, pMesh->precomputedLoopNormals[loop_index]);
	}
	else if ((pMesh->mpoly[lt->poly].flag & ME_SMOOTH) == 0) {  /* flat */
		if (pMesh->precomputedFaceNormals) {
			copy_v3_v3(r_no, pMesh->precomputedFaceNormals[lt->poly]);
		}
		else {
#ifdef USE_LOOPTRI_DETECT_QUADS
			const MPoly *mp = &pMesh->mpoly[lt->poly];
			if (mp->totloop == 4) {
				normal_quad_v3(
				        r_no,
				        pMesh->mvert[pMesh->mloop[mp->loopstart + 0].v].co,
				        pMesh->mvert[pMesh->mloop[mp->loopstart + 1].v].co,
				        pMesh->mvert[pMesh->mloop[mp->loopstart + 2].v].co,
				        pMesh->mvert[pMesh->mloop[mp->loopstart + 3].v].co);
			}
			else
#endif
			{
				normal_tri_v3(
				        r_no,
				        pMesh->mvert[pMesh->mloop[lt->tri[0]].v].co,
				        pMesh->mvert[pMesh->mloop[lt->tri[1]].v].co,
				        pMesh->mvert[pMesh->mloop[lt->tri[2]].v].co);
			}
		}
	}
	else {
		const short *no = pMesh->mvert[pMesh->mloop[loop_index].v].no;
		normal_short_to_float_v3(r_no, no);
	}
}

static void dm_ts_SetTSpace(
        const SMikkTSpaceContext *pContext, const float fvTangent[3], const float fSign,
        const int face_num, const int vert_index)
{
	//assert(vert_index >= 0 && vert_index < 4);
	SGLSLMeshToTangent *pMesh = (SGLSLMeshToTangent *) pContext->m_pUserData;
	const MLoopTri *lt;
	uint loop_index;

#ifdef USE_LOOPTRI_DETECT_QUADS
	if (pMesh->face_as_quad_map) {
		lt = &pMesh->looptri[pMesh->face_as_quad_map[face_num]];
		const MPoly *mp = &pMesh->mpoly[lt->poly];
		if (mp->totloop == 4) {
			loop_index = (uint)(mp->loopstart + vert_index);
			goto finally;
		}
		/* fall through to regular triangle */
	}
	else {
		lt = &pMesh->looptri[face_num];
	}
#else
	lt = &pMesh->looptri[face_num];
#endif
	loop_index = lt->tri[vert_index];

	float *pRes;

finally:
	pRes = pMesh->tangent[loop_index];
	copy_v3_v3(pRes, fvTangent);
	pRes[3] = fSign;
}

static void DM_calc_loop_tangents_thread(TaskPool * __restrict UNUSED(pool), void *taskdata, int UNUSED(threadid))
{
	struct SGLSLMeshToTangent *mesh2tangent = taskdata;
	/* new computation method */
	{
		SMikkTSpaceContext sContext = {NULL};
		SMikkTSpaceInterface sInterface = {NULL};

		sContext.m_pUserData = mesh2tangent;
		sContext.m_pInterface = &sInterface;
		sInterface.m_getNumFaces = dm_ts_GetNumFaces;
		sInterface.m_getNumVerticesOfFace = dm_ts_GetNumVertsOfFace;
		sInterface.m_getPosition = dm_ts_GetPosition;
		sInterface.m_getTexCoord = dm_ts_GetTextureCoordinate;
		sInterface.m_getNormal = dm_ts_GetNormal;
		sInterface.m_setTSpaceBasic = dm_ts_SetTSpace;

		/* 0 if failed */
		genTangSpaceDefault(&sContext);
	}
}

void BKE_mesh_add_loop_tangent_named_layer_for_uv(
        CustomData *uv_data, CustomData *tan_data, int numLoopData,
        const char *layer_name)
{
	if (CustomData_get_named_layer_index(tan_data, CD_TANGENT, layer_name) == -1 &&
	    CustomData_get_named_layer_index(uv_data, CD_MLOOPUV, layer_name) != -1)
	{
		CustomData_add_layer_named(
		        tan_data, CD_TANGENT, CD_CALLOC, NULL,
		        numLoopData, layer_name);
	}
}

/**
 * Here we get some useful information such as active uv layer name and search if it is already in tangent_names.
 * Also, we calculate tangent_mask that works as a descriptor of tangents state.
 * If tangent_mask has changed, then recalculate tangents.
 */
void BKE_mesh_calc_loop_tangent_step_0(
        const CustomData *loopData, bool calc_active_tangent,
        const char (*tangent_names)[MAX_NAME], int tangent_names_count,
        bool *rcalc_act, bool *rcalc_ren, int *ract_uv_n, int *rren_uv_n,
        char *ract_uv_name, char *rren_uv_name, short *rtangent_mask)
{
	/* Active uv in viewport */
	int layer_index = CustomData_get_layer_index(loopData, CD_MLOOPUV);
	*ract_uv_n = CustomData_get_active_layer(loopData, CD_MLOOPUV);
	ract_uv_name[0] = 0;
	if (*ract_uv_n != -1) {
		strcpy(ract_uv_name, loopData->layers[*ract_uv_n + layer_index].name);
	}

	/* Active tangent in render */
	*rren_uv_n = CustomData_get_render_layer(loopData, CD_MLOOPUV);
	rren_uv_name[0] = 0;
	if (*rren_uv_n != -1) {
		strcpy(rren_uv_name, loopData->layers[*rren_uv_n + layer_index].name);
	}

	/* If active tangent not in tangent_names we take it into account */
	*rcalc_act = false;
	*rcalc_ren = false;
	for (int i = 0; i < tangent_names_count; i++) {
		if (tangent_names[i][0] == 0) {
			calc_active_tangent = true;
		}
	}
	if (calc_active_tangent) {
		*rcalc_act = true;
		*rcalc_ren = true;
		for (int i = 0; i < tangent_names_count; i++) {
			if (STREQ(ract_uv_name, tangent_names[i]))
				*rcalc_act = false;
			if (STREQ(rren_uv_name, tangent_names[i]))
				*rcalc_ren = false;
		}
	}
	*rtangent_mask = 0;

	const int uv_layer_num = CustomData_number_of_layers(loopData, CD_MLOOPUV);
	for (int n = 0; n < uv_layer_num; n++) {
		const char *name = CustomData_get_layer_name(loopData, CD_MLOOPUV, n);
		bool add = false;
		for (int i = 0; i < tangent_names_count; i++) {
			if (tangent_names[i][0] && STREQ(tangent_names[i], name)) {
				add = true;
				break;
			}
		}
		if (!add && ((*rcalc_act && ract_uv_name[0] && STREQ(ract_uv_name, name)) ||
		             (*rcalc_ren && rren_uv_name[0] && STREQ(rren_uv_name, name))))
		{
			add = true;
		}
		if (add)
			*rtangent_mask |= (short)(1 << n);
	}

	if (uv_layer_num == 0)
		*rtangent_mask |= DM_TANGENT_MASK_ORCO;
}

/**
 * See: #BKE_editmesh_loop_tangent_calc (matching logic).
 */
void BKE_mesh_calc_loop_tangent_ex(
        const MVert *mvert,
        const MPoly *mpoly, const uint mpoly_len,
        const MLoop *mloop,
        const MLoopTri *looptri,
        const uint looptri_len,

        CustomData *loopdata,
        bool calc_active_tangent,
        const char (*tangent_names)[MAX_NAME], int tangent_names_len,
        const float (*poly_normals)[3],
        const float (*loop_normals)[3],
        const float (*vert_orco)[3],
        /* result */
        CustomData *loopdata_out,
        const uint  loopdata_out_len,
        short *tangent_mask_curr_p)
{
	int act_uv_n = -1;
	int ren_uv_n = -1;
	bool calc_act = false;
	bool calc_ren = false;
	char act_uv_name[MAX_NAME];
	char ren_uv_name[MAX_NAME];
	short tangent_mask = 0;
	short tangent_mask_curr = *tangent_mask_curr_p;

	BKE_mesh_calc_loop_tangent_step_0(
	        loopdata, calc_active_tangent, tangent_names, tangent_names_len,
	        &calc_act, &calc_ren, &act_uv_n, &ren_uv_n, act_uv_name, ren_uv_name, &tangent_mask);
	if ((tangent_mask_curr | tangent_mask) != tangent_mask_curr) {
		/* Check we have all the needed layers */
		/* Allocate needed tangent layers */
		for (int i = 0; i < tangent_names_len; i++)
			if (tangent_names[i][0])
				BKE_mesh_add_loop_tangent_named_layer_for_uv(loopdata, loopdata_out, (int)loopdata_out_len, tangent_names[i]);
		if ((tangent_mask & DM_TANGENT_MASK_ORCO) && CustomData_get_named_layer_index(loopdata, CD_TANGENT, "") == -1)
			    CustomData_add_layer_named(loopdata_out, CD_TANGENT, CD_CALLOC, NULL, (int)loopdata_out_len, "");
		if (calc_act && act_uv_name[0])
			BKE_mesh_add_loop_tangent_named_layer_for_uv(loopdata, loopdata_out, (int)loopdata_out_len, act_uv_name);
		if (calc_ren && ren_uv_name[0])
			BKE_mesh_add_loop_tangent_named_layer_for_uv(loopdata, loopdata_out, (int)loopdata_out_len, ren_uv_name);

#ifdef USE_LOOPTRI_DETECT_QUADS
		int num_face_as_quad_map;
		int *face_as_quad_map = NULL;

		/* map faces to quads */
		if (looptri_len != mpoly_len) {
			/* over alloc, since we dont know how many ngon or quads we have */

			/* map fake face index to looptri */
			face_as_quad_map = MEM_mallocN(sizeof(int) * looptri_len, __func__);
			int k, j;
			for (k = 0, j = 0; j < (int)looptri_len; k++, j++) {
				face_as_quad_map[k] = j;
				/* step over all quads */
				if (mpoly[looptri[j].poly].totloop == 4) {
					j++;  /* skips the nest looptri */
				}
			}
			num_face_as_quad_map = k;
		}
		else {
			num_face_as_quad_map = (int)looptri_len;
		}
#endif

		/* Calculation */
		if (looptri_len != 0) {
			TaskScheduler *scheduler = BLI_task_scheduler_get();
			TaskPool *task_pool;
			task_pool = BLI_task_pool_create(scheduler, NULL);

			tangent_mask_curr = 0;
			/* Calculate tangent layers */
			SGLSLMeshToTangent data_array[MAX_MTFACE];
			const int tangent_layer_num = CustomData_number_of_layers(loopdata_out, CD_TANGENT);
			for (int n = 0; n < tangent_layer_num; n++) {
				int index = CustomData_get_layer_index_n(loopdata_out, CD_TANGENT, n);
				BLI_assert(n < MAX_MTFACE);
				SGLSLMeshToTangent *mesh2tangent = &data_array[n];
				mesh2tangent->numTessFaces = (int)looptri_len;
#ifdef USE_LOOPTRI_DETECT_QUADS
				mesh2tangent->face_as_quad_map = face_as_quad_map;
				mesh2tangent->num_face_as_quad_map = num_face_as_quad_map;
#endif
				mesh2tangent->mvert = mvert;
				mesh2tangent->mpoly = mpoly;
				mesh2tangent->mloop = mloop;
				mesh2tangent->looptri = looptri;
				/* Note, we assume we do have tessellated loop normals at this point (in case it is object-enabled),
				 * have to check this is valid...
				 */
				mesh2tangent->precomputedLoopNormals = loop_normals;
				mesh2tangent->precomputedFaceNormals = poly_normals;

				mesh2tangent->orco = NULL;
				mesh2tangent->mloopuv = CustomData_get_layer_named(loopdata, CD_MLOOPUV, loopdata_out->layers[index].name);

				/* Fill the resulting tangent_mask */
				if (!mesh2tangent->mloopuv) {
				    mesh2tangent->orco = vert_orco;
				    if (!mesh2tangent->orco)
					    continue;

				    tangent_mask_curr |= DM_TANGENT_MASK_ORCO;
				}
				else {
				    int uv_ind = CustomData_get_named_layer_index(loopdata, CD_MLOOPUV, loopdata_out->layers[index].name);
				    int uv_start = CustomData_get_layer_index(loopdata, CD_MLOOPUV);
				    BLI_assert(uv_ind != -1 && uv_start != -1);
				    BLI_assert(uv_ind - uv_start < MAX_MTFACE);
				    tangent_mask_curr |= (short)(1 << (uv_ind - uv_start));
				}

				mesh2tangent->tangent = loopdata_out->layers[index].data;
				BLI_task_pool_push(task_pool, DM_calc_loop_tangents_thread, mesh2tangent, false, TASK_PRIORITY_LOW);
			}

			BLI_assert(tangent_mask_curr == tangent_mask);
			BLI_task_pool_work_and_wait(task_pool);
			BLI_task_pool_free(task_pool);
		}
		else {
			tangent_mask_curr = tangent_mask;
		}
#ifdef USE_LOOPTRI_DETECT_QUADS
		if (face_as_quad_map) {
			MEM_freeN(face_as_quad_map);
		}
#undef USE_LOOPTRI_DETECT_QUADS

#endif

		*tangent_mask_curr_p = tangent_mask_curr;

		/* Update active layer index */
		int act_uv_index = CustomData_get_layer_index_n(loopdata, CD_MLOOPUV, act_uv_n);
		if (act_uv_index != -1) {
		    int tan_index = CustomData_get_named_layer_index(loopdata, CD_TANGENT, loopdata->layers[act_uv_index].name);
		    CustomData_set_layer_active_index(loopdata, CD_TANGENT, tan_index);
		}/* else tangent has been built from orco */

		/* Update render layer index */
		int ren_uv_index = CustomData_get_layer_index_n(loopdata, CD_MLOOPUV, ren_uv_n);
		if (ren_uv_index != -1) {
		    int tan_index = CustomData_get_named_layer_index(loopdata, CD_TANGENT, loopdata->layers[ren_uv_index].name);
		    CustomData_set_layer_render_index(loopdata, CD_TANGENT, tan_index);
		}/* else tangent has been built from orco */
	}
}

void BKE_mesh_calc_loop_tangents(
        Mesh *me_eval, bool calc_active_tangent,
        const char (*tangent_names)[MAX_NAME], int tangent_names_len)
{
	BKE_mesh_runtime_looptri_ensure(me_eval);

	/* TODO(campbell): store in Mesh.runtime to avoid recalculation. */
	short tangent_mask = 0;
	BKE_mesh_calc_loop_tangent_ex(
	        me_eval->mvert,
	        me_eval->mpoly, (uint)me_eval->totpoly,
	        me_eval->mloop,
	        me_eval->runtime.looptris.array, (uint)me_eval->runtime.looptris.len,
	        &me_eval->ldata,
	        calc_active_tangent,
	        tangent_names, tangent_names_len,
	        CustomData_get_layer(&me_eval->pdata, CD_NORMAL),
	        CustomData_get_layer(&me_eval->ldata, CD_NORMAL),
	        CustomData_get_layer(&me_eval->vdata, CD_ORCO),  /* may be NULL */
	        /* result */
	        &me_eval->ldata, (uint)me_eval->totloop,
	        &tangent_mask);
}

/** \} */
